U.S. Pat. No. 4,104,019 discloses apparatus and method for fixation of dyes and other chemicals in textile fibers, however formed or combined, wherein the textile fibrous materials are wetted with dye or other chemicals and are continuously mechanically conveyed through a closely confined tube located between electrodes which create a radio frequency (RF) energy field in the tube. The fibrous material is packed within the tube during its passage therethrough so as to provide a partially self-sealing pressure chamber therein due to generation of steam whereby the rate of reaction of the dye or chemical on the fibers is accelerated.
As shown in FIG. 3 of the patent, loose fibrous materials are continuously conveyed by suitable conveyors to a liquid dye or chemical applicator unit. The fibers are gravitationally delivered by a chute into a liquid padding unit which contains a moving belt having an amount, or level, of liquid dye or chemical thereon. The liquid dye or chemical transfers into the fibrous material as it is fed into the nip portion of a double roller mangle comprising an upper drum and a lower drum over which the belt passes. The pressure of the roller mangle is controlled to express excess dye or chemical from the wetted fibers and obtain a desired wet pick-up, after which the fibers are further continuously directed into an elongate RF energy heating tube where they are compacted during heat fixation.
It is also known in such equipment as described in U.S. Pat. No. 4,104,019 to utilize a fiber-receiving hopper and ram assembly for receiving the wetted fibrous material from the padding unit and delivering the same under compression into the RF heating tube. The hopper has an open top for gravitationally receiving the wetted fibrous material in a continous stream, or flow, into a lower fiber compression chamber which communicates with the RF energy heating tube. A fluid-actuated ram cycles through the hopper compression chamber to compress and pack the fibrous material into and push it through the heating tube. The compressed fibrous material moving through the tube is heated by RF energy to react or fix the dye or chemical on the fibers, and the material leaves the heating tube against the action of a reduced back pressure piston, after which it is washed, dried and collected in suitable manner.
The apparatus and process above described provides the advantages of a continuous dyeing operation utilizing less energy consumption than the conventional discontinous batch dyeing operations heretofore employed in the prior art. Such apparatus and process also permits effective dyeing of textile fibrous materials with lesser amounts of dye liquid than the prior art batch dyeing operations.
As aforementioned, it has been one practice to continuously deliver the loose staple fibers to the liquid dye applicator unit by means of an inclined chute which gravitationally delivers the fibers into contact with viscous liquid dye composition on the moving belt of the dye applicator, after which the fibers pass through the nip of the double roller mangle. This action impregnates the fibers with dye and expresses excess dye from the fibers to obtain the desired dye pick up thereon. With such apparatus, it has been difficult to maintain a continuous flow and uniform distribution of loose staple length fibers through the dye applicator unit, particularly as the fibers pass into and through the viscous liquid dye and the nip of the roller mangle. Discontinuities in the feed of the loose fibers occur and can cause a build up of the fibers at the dye unit which precludes their passage through the mangle rollers. Such a build up of fibers necessitates interruption of the continuous dyeing operation to correct the situation, with corresponding loss of efficiency of the operation. In addition, if the fibers are fed at a non-uniform rate or are not uniformly distributed during their passage through the dye applicator unit, the fibers tend to be non-uniformly impregnated with dye.
One effort directed to alleviating the problem of discontinuous feed and non-uniform application of dye to the fibers on the aforementioned equipment has been the provision of a rotary screen vacuum drum for collecting and condensing the loose fibers in the form of a more cohesive web which is delivered onto a horizontal conveyor and thereafter gravitationally by a chute to the nip rollers and belt of the aforementioned dye applicator unit. Such apparatus and method of handling the fibers to permit improved impregnation of the same during their continuous movement through the applicator unit are described in detail in a copending, commonly assigned U.S. patent application Ser. No. 390,202 filed June 21, 1982, and now U.S. Pat. No. 4,472,850.